A review on different technical specifications of respiratory rate monitors

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 04 Issue: 04 | Apr-2015, Available @ http://www.ijret.org 424
A REVIEW ON DIFFERENT TECHNICAL SPECIFICATIONS OF
RESPIRATORY RATE MONITORS
Karthik Mohan Rao1
, B.G. Sudarshan2
1
PG Student, Department of Instrumentation Technology, RV College Of Engineering, Bengaluru, India
2
Associate Professor, Department of Instrumentation Technology, RV College Of Engineering, Bengaluru, India
Abstract
Respiratory Rate (RR) is a very important physiological parameter to be monitored in both healthy and critical condition, as it
gives meaningful information regarding their respiratory system performance as well as condition. Respiratory rate is an
important vital sign that can indicate progression of illness but to also predict rapid decline in health. For the purpose, non-
invasive monitoring systems are becoming more popular due to the self-evident increase in patient comfort. It can be hard to
predict respiratory failure as it can lead to life threatening condition within a short span of time. Thus it necessitates continuous
monitoring of respiratory activity and suitable monitoring equipment are developed which could be life-saving. The survey
incorporates non-obtrusive strategies and gadgets used to give data about respiratory rate. Many types of respiratory rate
monitors have been used for the measurement of the Respiration Rate. This review consists of seven types of Respiration Rate
monitors with different sensors. Respiration Rate monitor using Ultrasonic Sensor and Respiration Rate monitor using facial
tracking method are the non-contact respiration rate monitoring system. Respiration Rate measurement based on Impedance
Pneumography and Respiration Rate measurement are based on the Thoracic Expansion measurement include the sensor that are
placed on the thorax. Respiration Rate monitor with MEMS based Capacitive Pressure Sensor, Respiration Rate monitor with
temperature sensor, Respiration Rate meter–a low–cost design approach uses sensors that are mounted within the oxygen mask.
Thus the Respiratory Rate Monitors discussed in this paper provide optimal result to detect changes in the severity of chronic
illnesses.
Keywords: Respiratory Rate, RSA, RSS, Doppler Effect, Movement, Respiratory sensor belt.
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1. INTRODUCTION
Respiratory Rate (RR) is a very important physiological
parameter to be monitored in people both in healthy and
critical condition, as it gives meaningful information
regarding their respiratory system performance as well as
condition. The RR is defined as the number of breaths per
minute. A typical RR at resting is 12 and its corresponding
frequency is 0.2 Hz. During recovery from surgical
anesthesia, a µ-opioid agonists used for pain control can
slow down RR leading to bradypnea (RR<12) or even
apnea(cessation of respiration for an indeterminate
period)[13], while airway obstructions like asthma,
emphysema and COPD will increase RR causing
tachypnea(RR > 30)[14]. Hence, RR measurement becomes
clinically very important.
Changes in the severity of chronic illnesses such as Chronic
Obstructive Pulmonary Disease (COPD), Congestive Heart
Failure (CHF), Arthritis, Asthma, Cancer, Diabetes and
HIV/AIDS can be detected using Respiratory Rate Monitor.
Development of a respiration rate meter, a low-cost design
approach uses a displacement transducer with infrared (IR)-
transmitter and IR-receiver for sensing the Respiration
Rate[1]. Respiration Rate Monitor based on Impedance
Pneumography measures changes in the electrical
impedance of the person’s thorax caused by respiration or
breathing[2]. Respiratory Monitoring System Based on the
Thoracic Expansion Measurement uses respiratory sensor
belt that made up of plastic tube container, Axis, spring,
Bumper edge, reflective objective sensor[3]. Temperature
sensor based Breath Rate Monitor [4] is a real-time system
that computes the respiratory rate of the patient. The system
will activate an alarm on crossing the lower or upper
respiratory rate limit and simultaneously it will send a SMS
to the concerned doctor’s cell phone. This system uses a
temperature sensor to keep track of the temperature of the
respired air[4].
Facial Tracking Method for Noncontact Respiration Rate
Monitor involves tracking a facial region of interest (ROI)
associated with respiration in thermal images [5]. A new
Scheme of Respiration Rate Monitor uses a MEMS based
capacitive nasal sensor system for measuring Respiration
Rate (RR). Ultrasonic breathing monitor uses ultrasonic
source and transducer for the measurement of frequency
shift between the exhaled air flow and the ambient
environment[10].

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2. DIFFERENT TECHNICAL SPECIFICATIONS
OF RESPIRATORY RATE MONITORS
2.1 Development of a Respiration Rate Meter–A
Low–Cost Design Approach
The Respiration Rate meter uses a displacement transducer
in combination with infrared (IR) transmitter and IR –
receiver, respectively, for sensing the respiration rate. In the
capillary glass tube a thermocol ball moves up and down
during Inhaling and exhaling the air. The IR-transmitter and
receiver sense the ball movements. These movements are
converted into pulses by the pulse generator. A counter
counts these pulses for a minute. A 3-digit LED (Light
emitting diode) display monitors the respiration rate through
a 7-segment driver/decoder. To reset the display to initial
state (zero) and activate the counter for 1-minute to count
the respiration pulse, switch S1 (the start switch) is used.
The gate pulse generator utilises a monostable multivibrator
that generates gating pulse of 1-minute duration, when
triggered by start switch[1]. Fig -2 shows block diagram of
the system.
Fig -1: The sensor module [1]
Fig -2 The block diagram of the system [1]
2.2 Respiration Rate Measurement Based on
Impedance Pneumography
Impedance pneumography is a regularly utilized method to
screen a man's breath rate by housing two electrodes (Fig -
3A) or four electrodes (Fig -3B) on individual's thorax. The
goal of this approach is to quantify changes in the electrical
impedance of the individual's thorax created by breath or
relaxing. [2].
Fig -3: Arrangement of Electrodes for Impedance
Pneumography [2]
In both of these techniques, high-frequency ac current is
infused into tissue using drive electrodes. Potential
difference is produced over any two focuses between the
drive terminals because of ac current. Produced potential
difference is related to the tissue resistivity between receive
electrodes. The ratio of the difference in voltage between the
two receives electrodes and the current that permeates the
tissue is called equivalent resistance [2].
Fig -4: Principle Of Impedance Pneumography (Two-
electrode method).
The voltage difference measured across two electrodes in
two terminal measurement system generates some errors
(shown in Fig -3A) due to the presence of non-linear
voltage. The site of current infusion is set physically apart
from the potential measurement site in four electrode
system. Usage of four electrode system is less than
compared to two-electrode system due to the requirement of
additional two electrodes.

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2.3 Thoracic Expansion Measurement Based
Respiration Rate monitoring System
Thoracic Expansion Measurement Based Respiration Rate
monitoring System is specially designed for neonatal care
unit. The system is designed such that it has to work with
both group monitoring mode and individual monitoring
mode. The system works with group monitoring mode using
wireless transmission and with individual monitoring mode
using wired connection. The system needs following
specific designs: Respiratory sensor belt design, design of
the hardware and software design for the system. The
respiratory sensor belt is designed using reflective object
sensor. During the respiration, due to inhalation and
exhalation the thoracic or abdominal part expands. This
expansion results in the variation of output voltage of the
reflective object sensor. The Hardware part of the system is
designed such that it should allow the connection of the
respiration belt to individual monitoring mode or to group
monitoring mode. Finally, the software part consists of
algorithm that allows the connection of the respiration belt
to individual monitoring mode or to group monitoring
mode[3].
Fig -5: Graphic design and Logic symbol of the displaced
respiratory sensor
Graphic design and Logic symbol of the displaced
respiratory sensor is shown in the fig -5. The designed
respiratory sensor belt is named as PR2012. The respiratory
belt unit consists of constructed respiratory sensor. The
Respiratory belt is fastened firmly around the chest to
monitor the subject’s respiration rate[3].
2.4 Breath Rate Monitor using Non-invasive
Biosensor
The device is an intelligent system based on microcontroller.
The system will keep a nonstop authentic-time trace of the
respiratory rate of the patient. The system will give the
alarm on exceeding the respiratory rate boundary limit;
simultaneously system sends the SMS to the Physician
regarding the respiration rate. The system uses temperature
sensors to provide non-stop temperature response of the
respired air [4].
The framework utilizes LM-35 accuracy incorporated circuit
temperature sensors. Its yield voltage is relative to the
temperature which is measured in Celsius (Centigrade). The
scale component is 0.01 V/°C. The LM-35 has favourable
element over straight temperature sensors aligned in
°Kelvin, as it is not needed to subtract a vast steady voltage
from its yield to acquire advantageous Centigrade scaling. It
draws just 60µA from its supply[11]. Fig -6 demonstrates
the fundamental circuit of the LM-35.
Fig -6: Fundamental circuit of the Temperature sensor LM-
35
The microcontroller based framework utilizes brilliant
temperature sensor, which is set inside the breathing cover
or adjacent the nostrils of the patient concerned. This sensor
gives prompt temperature input of the breathed in and
breathed out air. To distinguish the maxima(s) and
minima(s), the microcontroller runs a calculation in
recursive mode, and in this manner concentrates its
periodicity. This framework is savvy enough to distinguish
false case recognition. The framework keeps a consistent
track of the respiratory rate and upgrades the rate for like
clockwork. The framework will give a caution, and sends a
SMS on the off chance that the respiratory rate surpasses the
limits of the lower or upper respiratory rate limit.
2.5 A Noncontact Respiration Rate Monitoring
System based on Facial Tracking Method
This method involves tracking a facial region of interest
(ROI) associated with respiration in thermal images. To
enhance the recorded thermal images and to remove
unwanted noise image processing techniques were used. The
skin surface area centered on the tip of the nose [fig -7] was
specified by a circle that covered the region affected by
respiration process. Signal processing and Feature extraction
methods were applied to this region to compute the
respiration rate[5].
Output
10.0 mV/°C
Basic Centigrade
Temperature sensor
+ Vs
(4V to 20V)
LM35

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FLIR A40 thermal camera is used to record the thermal
images. Thermal videos were recorded for two minutes for
each subject. This provided 6000 thermal images per
subject. To date, data from 15 subjects have been recorded,
but the data recordings are continuing. Following processes
are performed to find and track the ROI [7]:
i. Image enhancement
ii. Segmenting the subject face from the image background.
iii. Identification of the ROI
iv. Tracking the ROI
Fig -7: The position of ROI on the tip of the nose [5]
When the subject's face was extricated from the picture
foundation, the remaining range was uprooted. A scanning
operation was carried out inside the selected boundary. This
consisted of starting from the top-left corner of the boundary
and averaging the values of the pixels in an area consisting 5
by 5 pixels. This process continued till the scanning
operation reached the far right corner of the image. Then,
the scanning process was repeated by moving down by 5
pixels and then to the far left corner of the image again until
the selected area of the image was completely scanned.
During each scan, the most recently calculated average pixel
value was compared with the previous largest average pixel
value. If the current average value was larger the previous
value, it replaced the previous largest average pixel value[5].
2.6 A New Scheme for Determination of
Respiration Rate in Human Being using MEMS
Based Capacitive Pressure Sensor
The Scheme uses a MEMS based capacitive nasal sensor
system for measuring Respiration Rate (RR) of human
being. At first two identical diaphragms based MEMS
capacitive nasal sensors are designed and virtually
fabricated. The system consists of signal conditioning
circuitry along with the sensors. In order to measure the
respiration rate the sensors are mounted below Right Nostril
(RN) and Left Nostril (LN), in such a way that the nasal
airflow during inspiration and expiration impinge on the
sensor diaphragms as shown in the fig -8. Due to nasal
airflow, the designed square diaphragm of the sensor is
being deflected and thus induces a corresponding change in
the original capacitance value[9]. This change in capacitance
worth is to be distinguished by a connected twofold testing
(CDS) capacitance-to-voltage converter is intended for an
accuracy interface with MEMS capacitive weight sensor, a
speaker and a differential cyclic ADC to digitize the weight
data. The design of sensors and its characteristics analysis
are performed in a FEA/BEA based virtual simulation
platform[11]. The designed MEMS based capacitive nasal
sensors is capable of identifying normal RR (18.5±1.5 bpm)
of human being.
Fig -8: Schematic of the process for the respiration rate (RR)
measurement [9]
2.7 Breath Rate Monitoring System using
Ultrasonic Contactless Sensor
The system uses a low control ultrasonic dynamic source
and transducer. During the respiration there exists a
difference in the velocity of the expired air and surrounding
environment. This velocity difference will cause the
frequency shift. The device measures frequency shift, i.e.,
the Doppler shift (Doppler Effect). Obtained signal is then
digitized. Using a definite signal processing technique
effects of subject movements are separated from the breath.
The source is kept 50cm away from the sensor, and it uses
frequency of 40 kHz, well above audible frequencies[10].
The subject's head is illuminated with an acoustic wave
transmitted by a transducer and afterward that reflected
wave is recuperated and investigated. The subject's head is
to illuminated with an acoustic wave emitted by a transducer
and then that reflected wave is recovered and analyzed. A
frequency shift induced due to the movement of the subject
and also the exhaled air flow is known as Doppler
effect[10].
The apparatus permits checking the breathing of a subject in
recumbent position. A wide area including the subject's head
is illuminated using a 40 kHz ultrasound transmitter. The
receiver receives the reflected signal, and is recuperated and
investigated. The wave of incidence and movement of
neighbouring objects is subjected to different
transformations linked to physical and chemical
characteristics after the incidence of reflected wave on the
local environment of the media. The acquired deciding
result is a mixture of frequency shift, level reduction, and a
modified spectral energy repartition against time when the
subject inhales out. Fig -9 shows the block diagram of the
apparatus.

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Fig -9: Block diagram of the device [10]
3. COMPARISON BETWEEN TECHNICAL
SPECIFICATIONS OF DIFFERENT
RESPIRATION RATE MONITORS
Table -1: Comparison between technical specifications of
different Respiration Rate monitors
Types Sensor Module Methodology
Respiration
rate meter–a
low–cost
design
approach
Uses mask fitted
with IR LED
transmitter-
receiver[1] as
shown in the fig -
1
Movement of
thermocol ball
between IR
transmitter-
Receiver
produces pulse[1]
Respiration
Rate
Measurement
Based on
Impedance
Pneumography
Uses electrodes
that are placed on
the chest,
measures
electrical
impedance
changes of
thorax[2]
Impedance
Pneumography
Method[2]
Thoracic
Expansion
Measurement
Based
Respiration
Rate
monitoring
System
Uses
displacement
transducer,
constructed using
axis, spring,
bumper edge,
reflective object
sensor as shown
in the fig -5[3]
Displacement
method[3]
Breath Rate
Monitor using
Non-invasive
Biosensor
Uses temperature
sensor that
measures
temperature
changes during
inhalation-
exhalation[4]
Thermistor
method[4]
A Noncontact
Respiration
Rate
Monitoring
system based
on Facial
Tracking
Method
Uses thermal
camera to take the
thermal images
and movement of
ROI can be
measured using
image
processing[5].
Displacement
method, Image
processing[5].
A New
Scheme for
Determination
of Respiration
Rate in Human
Being using
MEMS Based
Capacitive
Pressure
Sensor
Uses MEMS
based capacitive
nasal sensors that
are mounted
below Right
Nostril (RN) and
Left Nostril[9].
Change of
capacitance
during the
exhalation-
inhalation
cycle[9].
Breath Rate
Monitoring
system using
Ultrasonic
Contactless
Sensor
Uses ultrasound
transmitter-
receiver to
measure the
subject's head
movement and
respiration air
movement using
an ultrasonic
wave[10].
Measurement of
movement of
both Subject and
exhaled air using
Doppler
effect[10].
4. CONCLUSION
Respiratory rate is one of the fundamental signs that are
viewed as standard for observing patients on intense clinic
wards. An irregular respiratory rate has demonstrated as a
critical indicator of genuine clinical occasions, for example,
Cardiac capture and admission to an emergency unit. There
are varieties of Respiration Rate monitors. In this paper,
seven types of Respiration Rate monitors are reviewed. And
each Respiration Rate monitor has its own specification with
different methodology. The Respiration Rate monitors
discussed in this paper uses methods such as Displacement
method, Thermistor method, image processing method,
capacitance method. All type of monitors discussed will
provide optimal result.
REFERENCES
[1]. Souvik Das, “Development of a Respiration Rate meter
–a low-cost design approach”, Health Informatics - An
International Journal (HIIJ) Vol.2, No.2, May 2013.
[2]. Amit K. Gupta, “Respiration Rate Measurement Based
on Impedance Pneumography”, Texas Instruments
Application report SBAA181–February 2011.
[3]. Fabiola Araujo Cespedes, “Respiratory Monitoring
System Based on the Thoracic Expansion Measurement”,
University of South Florida Scholar Commons, Graduate
Theses and Dissertations, January 2012.
[4]. Sumanta Bose, Prabu K, Dr. D. Sriram Kumar, “Real-
Time Breath Rate Monitor based Health Security System
using Non-invasive Biosensor”, Third International
Conference on Computing Communication & Networking
Technologies (ICCCNT), IEEE 2012.
[5]. F. Q. AL-Khalidi, and R. Saatchi, D. Burke and H.
Elphick, “Facial Tracking Method for Noncontact
Respiration Rate Monitoring”, 7th International Symposium
on Communication Systems Networks and Digital Signal
Processing (CSNDSP), IEEE 2010.

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[6]. Won Young Lee, Kyung Kwon Jung, Yong Joong Kim,
Gi Seop Lee, Cheol Gyu Park, “Implementation of Face
Tracking System for Non-contact Respiration Monitoring”,
International Conference on Future Information Technology
and Management Science & Engineering Lecture Notes in
Information Technology, Vol.14, 2012.
[7]. F.Q. AL-Khalidi, R. Saatchi, D. Burke, H. Elphick,
“Tracking human face features in thermal images for
respiration monitoring”, IEEE/ACS International
Conference on Computer Systems and Applications
(AICCSA), 2010.
[8]. “L-com’s HG2409P high performance directional flat
patch antenna,” http://www.l-com.com/wireless-antenna-24-
ghz-8-dbi-flat-patch-antenna-12in-n-female-connector.
[9]. Madhurima Chattopadhyay, Deborshi Chakraborty, “A
New Scheme for Determination of Respiration Rate in
Human Being using MEMS Based Capacitive Pressure
Sensor: Simulation Study”, Proceedings of the 8th
International conference on Sensing Technology, Sep 2014,
Liverpool, UK.
[10]. Philippe Arlotto, Michel Grimaldi, Roomila Naeck and
Jean-Marc Ginoux, “An Ultrasonic Contactless Sensor for
Breathing Monitoring”, Sensors 2014, 14(8), 15371-15386;
doi:10.3390/s140815371.
[11]. Milic-Emili J,“Recent advances in clinical assessment
of control of breathing”, Lung 1982, pp. 160:1–17.
[12]. D. Moffett, S. Moffett and C. Schauf, “Human
physiology”, 2nd
edition, Wm. C. Brown Publishers, 1993,
Ch. 13 and 16.
[13]. Ivana Prkic et al., “Pontine µ-opioid receptors mediate
bradypnea caused by intravenous remifentanil infusions at
clinically relevant concentrations in dogs,” J Neurophysiol
2012, vol.108, pp. 2430 –2441.
[14]. Weigt SS, Abrazado M, Kleerup EC, Tashkin DP,
Cooper CB, “Time course and degree of hyperinflation with
metronomepaced tachypnea in COPD patients,” COPD
2008, vol. Oct;5(5), pp.298-304. doi:
10.1080/15412550802363428.
BIOGRAPHIES
Karthik Mohan Rao received the B.E. degree in
Electronics and Comunication engineering from
Vivekananda college of Engineering Technology, Puttur,
India and pursuing M.Tech. degree in Biomedical Signal
Processing and Instrumentation engineering in RV College
Of Engineering, Bengaluru, India.
Dr. B.G. Sudharshan working as Associate Professor,
Department of Biomedical Signal Processing &
Instrumentation, RV College Of Engineering, Bengaluru,
India

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